1. Technical Field
The present invention relates to an optical element such as a transparent-type phase shifting mask in which a transfer pattern having a shield part, a light transmission part, and a phase shifter part is formed on a substrate, and relates to a manufacturing method of the same.
2. Description of Related Art
In recent years, an optical element such as a transparent-type phase shifting mask in which a transfer pattern having a shield part, a light transmission part, and a phase shifter part is formed on a substrate (for example, a transparent substrate such as quartz), is known (for example, see patent document 1). The shield part is formed by patterning a light shielding film formed on the substrate, so that light emitted to the optical element is blocked. The light transmission part is formed by partially exposing the surface of the substrate, so that the light emitted to the optical element is transmitted therethrough. The phase shifter part is formed by partially etching the exposed surface of the substrate, so that the light emitted to the optical element is transmitted therethrough while the phase of the light emitted to the optical element is shifted by a prescribed amount.    (Patent document 1) Japanese Patent Laid Open Publication No. 2003-330159
For example, a method shown in FIG. 1 is considered as a method of manufacturing the optical element.
First, an optical element blank 100b is prepared, with a light shielding film 102 and a first resist film 103 formed in this order on a substrate 101 (FIG. 1A). Then, by using a photolithography technique, a first resist pattern 103p covering an area excluding a formation scheduled area 110′ of a phase shifter part 110 (a formation scheduled area 111′ of a light transmission part 111 and a formation scheduled area 120′ of a shield part 120) is formed (FIG. 1B). Then, a partially exposed light shielding film 102 is etched and removed, with the formed first resist pattern 103p as a mask, and thereafter the surface of the substrate 101 partially exposed by etching the light shielding film 102 is etched by a prescribed depth, to thereby form the phase shifter part 110 (FIG. 1C). Then, the first resist pattern 103p is removed (FIG. 1D). Then, a second resist film 104 is formed so as to cover entire surfaces of the formation scheduled area 111′ of the light transmission part 111, the formation scheduled area 120′ of the shield part 120, and the phase shifter part 110 (FIG. 1E). Then, by using the photolithography technique, a second resist pattern 104p covering a formation scheduled area 120′ of the shield part 120 is formed (FIG. 1F). Then, the exposed light shielding film 102 is etched and removed, with the second resist pattern 104p as a mask, and the surface of the substrate 101 is partially exposed, to thereby form the light transmission part 111 (FIG. 1G). Then, the second resist pattern 104p is removed (FIG. 1H). Thus, the optical element 100 is manufactured, with the shield part 120, the light transmission part 111, and the phase shifter part 110 formed on the substrate 101.
Further, a method shown in FIG. 2, for example, is considered as other method of manufacturing the optical element.
First, an optical element blank 200b is prepared, with a light shielding film 202 and a first resist film 203 formed on a substrate 201 in this order (FIG. 2A). Then, by using the photolithography technique, a first resist pattern 203p covering a formation scheduled area 220′ of the shield part is formed (FIG. 2B). Then, the exposed light shielding film 202 is removed by etching, with the formed first resist pattern 203p as a mask (FIG. 2C). Then, the first resist pattern 203p is removed, and a shield part 220 is formed (FIG. 2D). Then, a second resist film 204 is formed so as to cover entire surfaces of the formation scheduled area 211′ of the light transmission part, the shield part 220, and formation scheduled area 210′ of the phase shifter part (FIG. 2E). Then, by using the photolithography technique, a second resist pattern 204p covering an area excluding the formation scheduled area 210′ of the phase shifter part 210 (the formation scheduled area 211′ of the light transmission part 211 and the shield part 220) is formed (FIG. 2F). Then, the surface of the exposed substrate 201 is etched by a prescribed depth, with the formed second resist pattern 204p as a mask, to thereby form the phase shifter part 210 (FIG. 2G). Then, the second resist pattern 204p is removed (FIG. 2H). Thus, an optical element 200 is manufactured, with the shield part 220, the light transmission part 211, and the phase shifter part 210 formed on the substrate 201.
In the aforementioned two methods, in each case, the shield part, the light transmission part, and the phase shifter part are demarcated by undergoing a photolithography step twice. For example, in a method shown in FIG. 1, the phase shifter part 110 is demarcated by undergoing a first photolithography step (step shown in FIG. 1B), and thereafter, a border between the shield part 120 and the light transmission part 111 is demarcated by undergoing second photolithography steps (steps shown in FIG. 1F). Further, in a method shown in FIG. 2, the shield part 220 is demarcated by undergoing the first photolithography step (step shown in FIG. 2B), and thereafter the border between the phase shifter part 210 and the light transmission part 211 is demarcated by undergoing the second photolithography step (step shown in FIG. 2F).
However, after a strenuous examination by inventors of the present invention, it is found that for example a relative position between the shield part and the phase shifter part is unintentionally shifted in some cases, when the shield part, the light transmission part, and the phase shifter part are respectively formed by undergoing the photolithography steps twice. Namely, in the aforementioned method, the step of removing a mask blank during processing, from a drawing apparatus once and forming the second resist film (for example, the step shown in FIG. 1E and FIG. 2E) needs to be executed, between the first photolithography step and the second photolithography step.
However, when the mask blank during processing is removed from the drawing apparatus once, an optical element blank is hardly installed on the drawing apparatus with good reproducibility. As a result, deviation of alignment can not be completely prevented from generating between a drawing result in the first photolithography step and a drawing result in the second photolithography step. Namely, when a positional deviation is generated in the mask blank re-installed on the drawing apparatus, in the method shown in FIG. 1, the relative position between the shield part 120 demarcated by the first photolithography step and the phase shifter part 110 demarcated by the second photolithography step (position of C with respect to A, Bin FIG. 5B) is deviated by about 10 to 30 nm with respect to the relative position in design. Similarly, in the method shown in FIG. 2 as well, the relative position between the shield part 220 demarcated by the first photolithography step and the phase shifter part 210 demarcated by the second photolithography step (positions of A, B with respect to C in FIG. 5C) is deviated by about 10 to 30 nm with respect to the relative position in design.